/* 
 * tsh - A tiny shell program with job control
 * 
 * <Put your name and login ID here>
 */
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <ctype.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <errno.h>

/* Misc manifest constants */
#define MAXLINE    1024   /* max line size */
#define MAXARGS     128   /* max args on a command line */
#define MAXJOBS      16   /* max jobs at any point in time */
#define MAXJID    1<<16   /* max job ID */

/* Job states */
#define UNDEF 0 /* undefined */
#define FG 1    /* running in foreground */
#define BG 2    /* running in background */
#define ST 3    /* stopped */

/* 
 * Jobs states: FG (foreground), BG (background), ST (stopped)
 * Job state transitions and enabling actions:
 *     FG -> ST  : ctrl-z
 *     ST -> FG  : fg command
 *     ST -> BG  : bg command
 *     BG -> FG  : fg command
 * At most 1 job can be in the FG state.
 */

/* Global variables */
extern char **environ;      /* defined in libc */
char prompt[] = "tsh> ";    /* command line prompt (DO NOT CHANGE) */
int verbose = 0;            /* if true, print additional output */
int nextjid = 1;            /* next job ID to allocate */
char sbuf[MAXLINE];         /* for composing sprintf messages */

struct job_t {              /* The job struct */
    pid_t pid;              /* job PID */
    int jid;                /* job ID [1, 2, ...] */
    int state;              /* UNDEF, BG, FG, or ST */
    char cmdline[MAXLINE];  /* command line */
};

// typedef struct job_t job_t;
struct job_t jobs[MAXJOBS]; /* The job list */

/* End global variables */


/* Function prototypes */

/* Here are the functions that you will implement */
void eval(char *cmdline);
int builtin_cmd(char **argv);
void do_bgfg(char **argv);
void waitfg(pid_t pid);

void sigchld_handler(int sig);
void sigtstp_handler(int sig);
void sigint_handler(int sig);

/* Here are helper routines that we've provided for you */
int parseline(const char *cmdline, char **argv); 
void sigquit_handler(int sig);

void clearjob(struct job_t *job);
void initjobs(struct job_t *jobs);
int maxjid(struct job_t *jobs); 
int addjob(struct job_t *jobs, pid_t pid, int state, char *cmdline);
int deletejob(struct job_t *jobs, pid_t pid); 
pid_t fgpid(struct job_t *jobs);
struct job_t *getjobpid(struct job_t *jobs, pid_t pid);
struct job_t *getjobjid(struct job_t *jobs, int jid); 
int pid2jid(pid_t pid); 
void listjobs(struct job_t *jobs);

void usage(void);
void unix_error(char *msg);
void app_error(char *msg);
typedef void handler_t(int);
handler_t *Signal(int signum, handler_t *handler);

/*
 * main - The shell's main routine 
 */
int main(int argc, char **argv) 
{
    char c;
    char cmdline[MAXLINE];
    int emit_prompt = 1; /* emit prompt (default) */

    /* Redirect stderr to stdout (so that driver will get all output
     * on the pipe connected to stdout) */
    dup2(1,2);

    /* Parse the command line */
    while ((c = getopt(argc, argv, "hvp")) != EOF) 
    {
        switch (c) 
        {
	        case 'h':             /* print help message */
	            usage();
		    break;
	        
	        case 'v':             /* emit additional diagnostic info */
	            verbose = 1;
		    break;
	        
	        case 'p':             /* don't print a prompt */
	            emit_prompt = 0;  /* handy for automatic testing */
		    break;
			
			default:
	            usage();
		}
    }

    /* Install the signal handlers */

    /* These are the ones you will need to implement */
    Signal(SIGINT,  sigint_handler);   /* ctrl-c */
    Signal(SIGTSTP, sigtstp_handler);  /* ctrl-z */
    Signal(SIGCHLD, sigchld_handler);  /* Terminated or stopped child */

    /* This one provides a clean way to kill the shell */
    Signal(SIGQUIT, sigquit_handler); 

    /* Initialize the job list */
    initjobs(jobs);

    /* Execute the shell's read/eval loop */
    while (1) 
    {
		/* Read command line */
		if (emit_prompt) 
		{
		    printf("%s", prompt);
		    fflush(stdout);
		}
		
		if ((fgets(cmdline, MAXLINE, stdin) == NULL) && ferror(stdin))
		    app_error("fgets error");
		
		if (feof(stdin))    /* End of file (ctrl-d) */
		{
		    fflush(stdout);
		    exit(0);
		}

		/* Evaluate the command line */
		eval(cmdline);
		
		fflush(stdout);
		fflush(stdout);
    } 

    exit(0); /* control never reaches here */
}
  
/* 
 * eval - Evaluate the command line that the user has just typed in
 * 
 * If the user has requested a built-in command (quit, jobs, bg or fg)
 * then execute it immediately. Otherwise, fork a child process and
 * run the job in the context of the child. If the job is running in
 * the foreground, wait for it to terminate and then return.  Note:
 * each child process must have a unique process group ID so that our
 * background children don't receive SIGINT (SIGTSTP) from the kernel
 * when we type ctrl-c (ctrl-z) at the keyboard.  
*/
void eval(char *cmdline)
{
	char *argv[MAXARGS]; /* Argument list execve() */
	char buf[MAXLINE];   /* Holds modified command line */
	int bg;              /* Should the job run in bg or fg? */
	pid_t pid;           /* Process id */
	

	strcpy(buf, cmdline);
	bg = parseline(buf, argv); 

	if (argv[0] == NULL)  
		return;                     /* Ignore empty lines */

	if (!builtin_cmd(argv)) 
	{
		sigset_t blockset;
		sigemptyset(&blockset);
		sigaddset(&blockset, SIGCHLD);
		sigprocmask(SIG_BLOCK, &blockset, NULL);


		if ((pid = fork()) == 0)     /* Child runs user job */
		{  
			//setpgid(0,0);      /*i don't wanna the subprocess to receive the sigint*/

			if(execve(argv[0],argv,environ)<0)        
			{
				printf("%s: Command not found.\n", argv[0]);
				exit(0);
			}

		}




		if (!bg)    //fg job
		{
			addjob(jobs,pid,FG,cmdline);
			sigprocmask(SIG_UNBLOCK, &blockset, NULL);
			waitfg(pid);
		}

		else         //bg job
		{
			addjob(jobs,pid,BG,cmdline);
			sigprocmask(SIG_UNBLOCK, &blockset, NULL);
			printf("[%d] (%d) %s", pid2jid(pid),pid, cmdline);
	    }
	    
    }

    return;
}

/* 
 * parseline - Parse the command line and build the argv array.
 * 
 * Characters enclosed in single quotes are treated as a single
 * argument.  Return true if the user has requested a BG job, false if
 * the user has requested a FG job.  
 */
int parseline(const char *cmdline, char **argv) 
{
    static char array[MAXLINE]; /* holds local copy of command line */
    char *buf = array;          /* ptr that traverses command line */
    char *delim;                /* points to first space delimiter */
    int argc;                   /* number of args */
    int bg;                     /* background job? */

    strcpy(buf, cmdline);
    buf[strlen(buf)-1] = ' ';  /* replace trailing '\n' with space, for check*/
    
    while (*buf && (*buf == ' ')) /* ignore leading spaces */
	buf++;

    /* Build the argv list */
    argc = 0;
    if (*buf == '\'') 
    {
		buf++;
		delim = strchr(buf, '\'');
    }

    else 
    {
		delim = strchr(buf, ' ');
    }

    while (delim) 
    {
		argv[argc++] = buf;
		*delim = '\0';
		buf = delim + 1;
		while (*buf && (*buf == ' ')) /* ignore spaces */
		       buf++;

		if (*buf == '\'') 
		{
		    buf++;
		    delim = strchr(buf, '\'');
		}
		else 
		{
		    delim = strchr(buf, ' ');
		}
    }
    
    argv[argc] = NULL;
    
    if (argc == 0)  /* ignore blank line */
	return 1;

    /* should the job run in the background? */
    if ((bg = (*argv[argc-1] == '&')) != 0) 
    {
		argv[--argc] = NULL;
    }

    return bg;
}

/* 
 * builtin_cmd - If the user has typed a built-in command then execute
 *    it immediately.  
 */
int builtin_cmd(char **argv) 
{
    if (!strcmp(argv[0], "quit")) /* quit command */
    	exit(0);

	if(!strcmp(argv[0], "bg") || !strcmp(argv[0], "fg"))
	{
		do_bgfg(argv);
		return 1;
	}

    if (!strcmp(argv[0], "&"))    /* Ignore singleton & */
    	return 1;
    

    if(!strcmp(argv[0],"jobs"))
    {
    	listjobs(jobs);
    	return 1;
    }

    return 0;                     /* Not a builtin command */
}

/* 
 * do_bgfg - Execute the builtin bg and fg commands
 */
void do_bgfg(char **argv) 
{
	int jid=0;
	int pid=0;
	const char * str_number;
	struct job_t * job;
	char *first_cmd = argv[0];
	char *second_cmd = argv[1];
	char e;

	const char *err_msg1 = "%s command requires PID or %%jobid argument\n";
	const char *err_msg2 = "%s argument must be a PID or %%jobid\n";
	const char *err_msg3 = "%s: No such job\n";
	const char *err_msg4 = "(%d): No such process\n";

	if(second_cmd==NULL)        /* if there is no index*/
    {
		printf(err_msg1, first_cmd);
		return;
    }

	if(second_cmd[0]=='%')       /* if begins with '%'，then it is a jobid */
	{
		str_number = strtok(second_cmd, "%");       /* delete the '%' */
		for(long unsigned i=0;i<strlen(str_number);i++)
		{
			e = str_number[i];

			if(e<'0'||e>'9')           /*if there is someting which is not number*/
			{
				printf(err_msg2, first_cmd);
				return;
			}
		}

		jid = atoi(str_number);        /* string -> int */
		job = getjobjid(jobs, jid);

		if(!job)                      /* if job doesn't existed */
		{
			printf(err_msg3, second_cmd);
			return;
		}
		
		else
		{               
			pid = job->pid;   /* extract the pid  */
		}
    }


	else
	{
		for(long unsigned i=0;i<strlen(second_cmd);i++)
		{
			e = second_cmd[i];

			if(e<'0'||e>'9')
			{
				printf(err_msg2, first_cmd);
				return;
			}
		}
		pid = atoi(second_cmd);
		job = getjobpid(jobs, pid);
		if(!job)
		{
			printf(err_msg4, pid);
			return;
		}
    }
    
	kill(-pid, SIGCONT);           /*whatever it is a "bg" or "fg", the job is going to run */
	
	if(!strcmp(first_cmd, "bg"))     /* bg */
	{
		job->state = BG;
		printf("[%d] (%d) %s", jid, pid, job->cmdline);
	}

	else      /*fg*/
	{
		job->state = FG;
		waitfg(job->pid);      /* what the hell...*/
	}

 	return;
}
/* 
 * waitfg - Block until process pid is no longer the foreground process
 */
void waitfg(pid_t pid)
{

 /*   int status;
    if (waitpid(pid, &status, WUNTRACED) < 0)
    	unix_error("waitfg: waitpid error");*/

/******************************************************/

	while(pid == fgpid(jobs))
	{
		sleep(0.5);
		// printf("i am waiting for the fg process\n");
	}
	if(verbose)
		printf("waitfg: Process (%d) no longer the fg process\n", pid);
/*
	struct job_t *job;
	job = getjobpid(jobs, pid);

	while(1)
	{
		pause();
		if((job->pid == 0 && job->state == UNDEF) || (job->pid == pid && job->state == ST))
		{
			if(verbose)
				printf("waitfg: Process (%d) no longer the fg process\n", pid);
			break;
		}
	}
*/
	return;
}

/*****************
 * Signal handlers
 *****************/

/* 
 * sigchld_handler - The kernel sends a SIGCHLD to the shell whenever
 *     a child job terminates (becomes a zombie), or stops because it
 *     received a SIGSTOP or SIGTSTP signal. The handler reaps all
 *     available zombie children, but doesn't wait for any other
 *     currently running children to terminate.  
 */
void sigchld_handler(int sig)
{
	if(verbose) printf("sigchld_handler is entering\n");
	// printf("a subprocess is finished\n");
	pid_t pid;
	int status;
	struct job_t *job;

	while((pid = waitpid(-1, &status, WUNTRACED|WNOHANG))>0)    /*to see which process is exited or stopped */
	{
		if(WIFEXITED(status))	      /* normal exit*/
		{
			// printf("Job [%d] (%d) exit\n", pid2jid(pid), pid);
			if(deletejob(jobs,pid))
			{
				if(verbose) printf("sigchld_handler: Job [%d] (%d) deleted\n",pid2jid(pid),pid);
			}
			else app_error("can't delete the job");
		}

		if(WIFSIGNALED(status))	      /* terminated by a signal */
		{
			if(deletejob(jobs, pid))
			{
				if(verbose) printf("sigchld_handler: Job [%d] (%d) deleted\n",pid2jid(pid),pid);
			}
			else app_error("can't delete the job");
			printf("Job [%d] (%d) terminated by signal %d\n", pid2jid(pid), pid, WTERMSIG(status));
		}

		if(WIFSTOPPED(status))	      /* stopped by a signal */
		{
			printf("Job [%d] (%d) stopped by signal %d\n", pid2jid(pid), pid, WSTOPSIG(status));
			job = getjobpid(jobs, pid);
			job->state=ST;
		}
    }
}




/* 
 * sigint_handler - The kernel sends a SIGINT to the shell whenver the
 *    user types ctrl-c at the keyboard.  Catch it and send it along
 *    to the foreground job.  
 */
void sigint_handler(int sig)
{
	if(verbose) printf("sigint_handler:entering\n");
	/* printf("receive a sigint\n");
    return;*/

	pid_t fpid;
	fpid = fgpid(jobs);
	// printf("interrupt the pid:%d\n", fpid);
	if(fpid)
	{
		kill(-fpid, sig);
		if(verbose) printf("sigint_handler: Job (%d) killed\n", fpid);
	}

	if(verbose) printf("sigint_handler:exiting\n");
	return;
}

/*
 * sigtstp_handler - The kernel sends a SIGTSTP to the shell whenever
 *     the user types ctrl-z at the keyboard. Catch it and suspend the
 *     foreground job by sending it a SIGTSTP.  
 */
void sigtstp_handler(int sig) 
{
	if(verbose) printf("sigtstp_handler:entering\n");

	/*printf("receive a sigtstp\n");
    return;*/
	pid_t fpid;
	fpid = fgpid(jobs);
	if(fpid)
	{
		kill(-fpid, sig);
		if(verbose) printf("sigtstp_handler: Job [%d] (%d) stopped\n",pid2jid(fpid),fpid);
	}
	if(verbose) printf("sigtstp_handler:exiting\n");
	return;
}

/*********************
 * End signal handlers
 *********************/

/***********************************************
 * Helper routines that manipulate the job list*
 ***********************************************/

/* clearjob - Clear the entries in a job struct */
void clearjob(struct job_t *job) {
    job->pid = 0;
    job->jid = 0;
    job->state = UNDEF;
    job->cmdline[0] = '\0';
}

/* initjobs - Initialize the job list */
void initjobs(struct job_t *jobs) {
    int i;

    for (i = 0; i < MAXJOBS; i++)
	clearjob(&jobs[i]);
}

/* maxjid - Returns largest allocated job ID */
int maxjid(struct job_t *jobs) 
{
    int i, max=0;

    for (i = 0; i < MAXJOBS; i++)
		if (jobs[i].jid > max)
		    max = jobs[i].jid;
    return max;
}

/* addjob - Add a job to the job list */
int addjob(struct job_t *jobs, pid_t pid, int state, char *cmdline) 
{
    int i;
    
    if (pid < 1)
	return 0;

    for (i = 0; i < MAXJOBS; i++) 
    {
		if (jobs[i].pid == 0)      // find a vacant position
		{
		    jobs[i].pid = pid;
		    jobs[i].state = state;
		    jobs[i].jid = nextjid++;    //nextjid increase 1
		    
		    if (nextjid > MAXJOBS)
				nextjid = 1;

		    strcpy(jobs[i].cmdline, cmdline);
	  	    
	  	    if(verbose)
	  	    {
		        printf("Added job [%d] %d %s\n", jobs[i].jid, jobs[i].pid, jobs[i].cmdline);
		    }
		    
		    return 1;
		}
    }
    printf("Tried to create too many jobs\n");
    return 0;
}

/* deletejob - Delete a job whose PID=pid from the job list */
int deletejob(struct job_t *jobs, pid_t pid) 
{
    if (pid < 1)
		return 0;

    for (int i = 0; i < MAXJOBS; i++) 
    {
		if (jobs[i].pid == pid)
		{
		    clearjob(&jobs[i]);
		    nextjid = maxjid(jobs)+1;   
		    return 1;
		}
    }
    return 0;
}

/* fgpid - Return PID of current foreground job, 0 if no such job */
pid_t fgpid(struct job_t *jobs) {
    
    int i;
    for (i = 0; i < MAXJOBS; i++)
	if (jobs[i].state == FG)
	    return jobs[i].pid;
    return 0;
}

/* getjobpid  - Find a job (by PID) on the job list */
struct job_t *getjobpid(struct job_t *jobs, pid_t pid) {
    int i;

    if (pid < 1)
	return NULL;
    for (i = 0; i < MAXJOBS; i++)
	if (jobs[i].pid == pid)
	    return &jobs[i];
    return NULL;
}

/* getjobjid  - Find a job (by JID) on the job list */
struct job_t *getjobjid(struct job_t *jobs, int jid) 
{
    int i;

    if (jid < 1)
	return NULL;
    for (i = 0; i < MAXJOBS; i++)
	if (jobs[i].jid == jid)
	    return &jobs[i];
    return NULL;
}

/* pid2jid - Map process ID to job ID */
int pid2jid(pid_t pid) 
{
    int i;

    if (pid < 1)
	return 0;
    for (i = 0; i < MAXJOBS; i++)
		if (jobs[i].pid == pid) 
		{
			return jobs[i].jid;  
		}
    return 0;
}

/* listjobs - Print the job list */
void listjobs(struct job_t *jobs)
{
    for (int i = 0; i < MAXJOBS; i++) 
    {
		if (jobs[i].pid != 0)
		{
		    printf("[%d] (%d) ", jobs[i].jid, jobs[i].pid);
		    switch (jobs[i].state) 
		    {
				case BG: 
				    printf("Running ");
				    break;
				case FG: 
				    printf("Foreground ");
				    break;
				case ST: 
				    printf("Stopped ");
				    break;
			    
			    default:
				    printf("listjobs: Internal error: job[%d].state=%d ", 
					   i, jobs[i].state);
		    }
		    printf("%s", jobs[i].cmdline);
		}
    }
}
/******************************
 * end job list helper routines
 ******************************/


/***********************
 * Other helper routines
 ***********************/

/*
 * usage - print a help message
 */
void usage(void) 
{
    printf("Usage: shell [-hvp]\n");
    printf("   -h   print this message\n");
    printf("   -v   print additional diagnostic information\n");
    printf("   -p   do not emit a command prompt\n");
    exit(1);
}

/*
 * unix_error - unix-style error routine
 */
void unix_error(char *msg)
{
    fprintf(stdout, "%s: %s\n", msg, strerror(errno));
    exit(1);
}

/*
 * app_error - application-style error routine
 */
void app_error(char *msg)
{
    fprintf(stdout, "%s\n", msg);
    exit(1);
}

/*
 * Signal - wrapper for the sigaction function
 */
handler_t *Signal(int signum, handler_t *handler) 
{
    struct sigaction action, old_action;

    action.sa_handler = handler;  
    sigemptyset(&action.sa_mask); /* block sigs of type being handled */
    action.sa_flags = SA_RESTART; /* restart syscalls if possible */

    if (sigaction(signum, &action, &old_action) < 0)
	unix_error("Signal error");
    return (old_action.sa_handler);
}

/*
 * sigquit_handler - The driver program can gracefully terminate the
 *    child shell by sending it a SIGQUIT signal.
 */
void sigquit_handler(int sig) 
{
    printf("Terminating after receipt of SIGQUIT signal\n");
    exit(1);
}



